1. Field of the Invention
This invention relates to pulsation dampeners or desurgers which dampen pressure fluctuations in piping, and in particular to such pulsation dampeners suitable for use under conditions of high temperature, high pressure, and sterility in the food-processing, pharmaceutical, and semi-conductor industries.
2. Description of the Related Art
Left unchecked, pressure pulsations from positive-displacement pumps and from rapidly-closing valves can cause a variety of problems in a piping system. Among these problems are inaccurate readings from on-line measuring devices, inaccurate performance by on-line metering systems, high levels of vibration, and in some cases even component failure. Rapid fluctuations in line pressure may exceed the response time of gauges and metering systems, resulting in erroneous readings and output signals. Filter systems are also susceptible to damage from pressure spikes and surges; larger particles may be forced through the filtration medium, and filter elements can be ruptured by undampened pressure surges.
Pulsation dampeners absorb pump pulsations and pressure surges (due to, e.g., valve ckisyres) reducing the amplitude of pressure fluctuations in the piping system. Types of pulsation dampeners include accumulators, which may be of the through-flow type or may be attached to the piping system as an appendage. Accumulators typically retain some of the material flowing through the system, leading to contamination problems as described below. Another type of pulsation dampener is the in-line type; the present invention is in this category. "Desurger," as used herein, refers to an in-line pulsation dampener.
Generally all pulsation dampeners include a bladder or diaphragm defining a gas-filled chamber which fluctuates in volume in response to changes in line pressure. Surges in line pressure compress gas in the chamber and cause the gas volume to decrease; the dampening is efficient because the gas volume is equivalent to a much larger volume of liquid. Desurgers may be attached to a line as an appendage which is linked to the line via a connection, or may be of the in-line type, in which the entire line contents flow through the desurger.
One problem with accumulator-type pulsation dampeners is the material retained within the accumulator between surges. In some piping systems the interval between surges may be several hours or longer, especially where the surges are caused by valve closures. These long intervals allow deterioration of material trapped in the accumulator chamber, and in some cases even bacterial growth. Subsequent surges replace some of the aged material in the accumulator chamber with new material; the material flushed from the chamber is mixed with and contaminates product flowing through the piping system.
Another problem is that previous desurgers were restricted to maximum operating temperatures well below the boiling point of water, with only intermittent use at higher temperatures. For liquids at higher temperatures, a desurger had to be connected as an appendage to the line being protected. This type of connection requires a section of liquid-filled pipe which forms a barrier or "cold seal" between the hot line and the desurger. The problem inherent with this arrangement, however, is similar to that described for accumulator-type dampeners; liquid from the cold seal section is periodically mixed with and introduced into the main product line. In high-sterility systems for processing food products and pharmaceuticals, etc., such mixing is unacceptable.
The problem addressed by the present invention is how to adapt desurgers for use in the food and pharmaceutical industries, and in other applications which require processing under conditions ensuring sterility.